Tokkai Hei 6-129509 published by the Japanese Patent Office in 1994 discloses a toroidal continuously variable transmission of a dual cavity-half toroidal type for vehicles.
This transmission comprises a pair of toroidal units disposed on the same input shaft. In each unit, a pair of power rollers are gripped between an input disk and an output disk disposed facing each other on the input shaft. The input disk rotates together with the input shaft, and the power rollers gripped between the input disk and output disk transfer a torque to the output disk by friction. Each power roller is supported by trunnions via a pivot shaft. The trunnions comprise a trunnion shaft which makes a right angle with the input shaft.
If the trunnion is displaced in the direction of the trunnion shaft, the contact point of the power roller with each disk will change, and the direction of the force exerted by each disk on the power roller will vary. Due to the variation of this force, the power roller undergoes a rotational displacement together with the trunnion shaft, and as a result, the contact radius of either the input disk or output disk increases, and that of the other disk decreases.
The variation of these contact radii causes the speed ratio of the input disk and output disk, i.e., the speed ratio of the transmission, to vary.
Thus, the speed ratio of the transmission can be continuously varied by displacing a trunnion in the direction of the trunnion shaft. The rotation angle of the power roller supported on the trunnion shaft as fulcrum is referred to for example as the gyration angle of the power roller, and directly corresponds to the speed ratio of the continuously variable transmission.